BILATERAL CONVERGENCE NYSTAGMUS IN UNILATERAL DORSAL MIDBRAIN STROKE DUE TO OCCLUSION OF THE SUPERIOR CEREBELLAR ARTERY

The authors report a 33-year-old man with left dorsal pontomesencephal ic and cerebellar infarction due to an angiographically verified left superior cerebellar artery (SCA)-occlusion. Clinical presentation incl uded dysarthria, homolateral limb ataxia, gait ataxia and controlatera l spinothalamic sensory loss. Additionally, skew deviation, bilateral convergence nystagmus and pseudo-sixth nerve palsy of the left eye wer e observed. Vertical gaze and pupillary light reactions were preserved . This observation expands the spectrum of eye movement abnormalities due to midbrain involvement in isolated SCA-stroke and confirms a mese ncephalic tectal territory of irrigation supplied by this artery. Addi tionally, it might give further evidence for the hypothesis of premoto r control of convergence at a higher than mesencephalic level.